Known gauge assemblies 20, such as illustrated in FIGS. 1 and 2 and disclosed in U.S. Pat. No. 5,479,820 to Fekete include a known dial assembly 22 and a known float assembly 24. Together, the dial assembly and float assembly produce a complete gauge assembly. For additional details, U.S. Pat. No. 5,479,820 to Fekete is hereby incorporated by reference herein in its entirety.
Referring now to FIGS. 1 and 2, for background, a known float assembly 24 has two major components: lift assembly 26 and a gauge head 28. The gauge head 28 defines a passageway 30 having a first end 32 and a second end 34 and is provided with threads 36 adjacent the second end 34 for screwing the gauge head 28 onto a wall of a vessel (shown in phantom in FIG. 1 only). Passageway 30 of gauge head 28 receives the upper portion of lift assembly 26 in a slidable fashion.
A known lift assembly 26 includes a lift rod 38 with a first end 40 and a second end 42 and a float 44 or displacement member, is coupled to the second end 42 of the lift rod 38 in a manner such that a movement of the float 44 induces a resulting motion of the lift rod 38 along longitudinal axis of the passageway 30 of the gauge head 28. Attached at the first end of the lift rod 38 is a lift magnet 46. The passageway 30 of the gauge head 28 receives the first end of the lift rod 38 and the lift magnet 46 attached thereto. As a liquid level in a vessel changes, the float 44 changes position. This in turn moves the lift rod 38 of the lift assembly 26 and thereby the lift magnet 46 along an axis of the passageway 30. Preferably, the first end 40 of the lift rod 38 has a bearing or camming surface 48 for sliding contact with the wall of passageway 30. Bearing surface 48 does not have to be in contact with the wall of passageway, and preferably, a space is provided between the upper end of lift rod 38 and the wall of the passageway 30 to allow for easy movement.
A known dial assembly 22 includes a casing 50 or base having a first side 52, including a dial face (not illustrated) having volume indicia (not illustrated), and a second side 54 having an attachment means 55 for attaching the dial assembly 22 to a gauge head 28. A pointer assembly 60 having a pointer 62 and pointer magnet 64 is rotatably mounted on a pivot pin 66 on the first side 52 of the dial assembly 22. The known dial assembly 22 attaches to a gauge head 28 such that the pointer magnet 64 and the lift magnet 46 are magnetically coupled, whereby a movement of the lift magnet 46 (induced by a movement of the lift rod 38 in the vertical direction induced by a movement of the float 44 as the fluid level in a vessel changes) induces a movement of the pointer magnet 64 which thereby repositions the pointer 62 relative to volume indicia on the dial face.
The known gauge assembly 20 has two calibration features that allow the gauge to be used with different types of fluids. One feature is adjusting the float 44 position at different positions relative to the lift rod 38 and the second feature is adjusting a position of the known dial assembly 22 relative to the gauge head 28. The first feature is most useful prior to attachment of the gauge assembly 22 to the vessel and is set with respect to the fluid to be measured. Once the gauge assembly is mounted to a vessel, it is inconvenient to remove it for adjustment. Thus, a second calibration feature which does not require removal of the gauge assembly has been used.
As illustrated in FIG. 1, the second feature is an adjustment nut 68. The known dial assembly 22 is calibrated by turning the nut 68 attached to a threaded upper portion of the known gauge head 28 thereby raising or lowering the pointer magnet 64 of the known dial assembly 22 relative to the lift magnet 46 of the known float assembly 24.
The disadvantage of this approach is that it requires the upper end of the gauge head 28 to be threaded and have an adjustment feature. Most conventional heads do not have threads on the outer portion to receive the dial adjustment feature of the Fekete device. Thus, there has been a need for a method and apparatus which permits calibration of the dial assembly which does not require a specially threaded gauge head. Another disadvantage of the gauge illustrated in FIG. 1 is that the adjustment nut 68 is highly visible and users may mistakenly turn the nut thinking it is for a purpose other than calibration and unintentionally change the gauge calibration.
While development of alternate methods of positioning a dial assembly 22 vertically relative to the gauge head 28 are also possible without modification to the gauge head 28, these methods may require significant additional room in the dial assembly 22 and add several complex, easily misaligned, exposed parts to the assembly. Further, the size of the known dial assembly is limited by the constraints of the particular dimensions of any one particular vessel or for use with one particular float assembly for which it was designed.
Thus, there is a need for a dial assembly that can be quickly and easily calibrated, recalibrated while positioned on a vessel, and which can be used with any known gauge head and any known float assembly, on any of a variety of dimensioned vessels, and with any of a variety of liquids with different densities without requiring repositioning of the dial assembly relative to the gauge head and without requiring modification to the gauge head.